Surface chemistry-microstructure-rheology of high and low crystallinity KGa-1b and KGa-2 kaolinite suspensions

This study investigated the surface chemistry-microstructure-rheology relationship of two very well characterised, low impurity CMS source kaolinites; low defect KGa-1b and high defect KGa-2. The knowledge gained will improve the overall understanding by acting as a reference material for comparison with other studies. The trend of the yield stress-pH result was adopted to investigate kaolinite properties or factors that affect this trend. Both the KGa-1b and KGa-2 kaolinite slurries displayed similar zeta potential-pH and yield stress-pH behaviour. Crystallinity and particle size therefore did not affect the trend of the yield stress-pH and zeta potential-pH behaviour. The larger yield stress of the finer KGa-2 slurries is due to a higher particle concentration. Both kaolinite slurries exhibited a maximum yield stress at zero zeta potential. Their yield stress-solid volume fraction data were found to obey a power law model with the same exponent value of 3 accounting for a fractal dimension of 2.3 unaffected by pH. Cryo-SEM images of the vitrified microstructure of 35 wt% KGa-1b and 15 wt% KGa-2 suspensions at the maximum yield stress showed a 3-D microstructure formed by compacted clay aggregates which themselves are formed by a mixture of particle interaction configurations - face-face with stair-step feature and edge-face. Particle interaction modelling was discussed. (C) 2015 Elsevier B.V. All rights reserved.